Infants' or youth's beds and hospital beds have long been provided with movable side rails for protecting the occupant from leaving the bed, with resultant possible injury. Such devices heretofore known are a permanent fixture on the bed and may be manipulated from up to down position or vice versa either by sliding vertical movement or by rotation on a horizontal axis. Such devices are subject to the objection that they are expensive, adding materially to the initial cost of the bed. In the case of infants' cribs, furthermore, they cannot be dispensed with after the child has outgrown the need for the protection without major mechanical reconstruction.